1. Field of the Invention
The present invention dates to delivery methods, systems and components thereof for use with hazardous or toxic pharmaceutical substances, and especially to delivery and injection methods, systems and components thereof for use with radiopharmaceutical substances.
2. Prior Art
As used herein, the term “pharmaceutical” refers to any substance to be injected or otherwise delivered, into the body (either human or animal) in a medical procedure and includes, but is not limited to, substances used in imaging procedures (for example, contrast media) and therapeutic substances. A number of such pharmaceutical substances pose a danger to both the patient and the personnel administering the substance if not handled and/or injected properly. Examples of hazardous pharmaceuticals include, but are not limited to, radiopharmaceuticals, biological pharmaceuticals, chemotherapeutic pharmaceuticals and gene therapeutic pharmaceuticals.
Examples of use of a radiopharmaceutical include positron emission tomography (PET) and single-photon emission computerized tomography (SPECT), which are noninvasive, three-dimensional, imaging procedures that provide information regarding physiological and biochemical processes in patients. The first step in producing PET images or SPECT images of, for example, the brain or another organ, is to inject the patient with a dose of the radiopharmaceutical. The radiopharmaceutical is generally a radioactive substance that can be absorbed by certain cells in the brain or other organ, concentrating it there. For example, fluorodeoxyglucose (FDG) is a normal molecule of glucose, the basic energy fuel of cells, attached a radionuclide or radioactive fluor. The radionuclide is produced in a cyclotron equipped with a unit to synthesize the FDG molecule.
Cells (for example, in the brain) which are more active in a given period of time after an injection of FDG, will absorb more FDG because they have a higher metabolism and require more energy. The radionuclide in the FDG molecule suffers a radioactive decay, emitting a positron. When a positron collides with an electron, an annihilation occurs, liberating a burst of energy in the form of two beams of gamma rays in opposite directions. The PET scanner detects the emitted gamma rays to compile a three dimensional image.
In that regard, after injecting the radiopharmaceutical, the patient is typically placed on a moveable bed which slides by remote control into a circular opening of the scanner referred to as the gantry. Positioned around the opening, and inside the gantry, there are several rings of radiation detectors. Each detector emits a brief pulse of light every time it is struck with a gamma ray coming from the radionuclide within the patient's body. The pulse of light is amplified, by a photomultiplier, and the information is sent to the computer which controls the apparatus.
The timing of injection is very important. After the generation of the radiopharmaceutical, a countdown begins. After a certain time, which is a function of the half-life of the radionuclide, the radiation level of the radiopharmaceutical dose falls exactly to a level required for the measurement by the scanner. In current practice, the radiation level of the radiopharmaceutical volume or dose is typically measured using a dose calibrator. Using the half-life of the radionuclide, the time that the dose should be injected to provide the desired level of radioactivity to the body is calculated. When that time is reached, the radiopharmaceutical dose is injected using a manually operated syringe.
Most PET radionuclides have short half-lives. Under proper injection procedures, these radionuclides can be safely administered to a patient in the form of a labelled substrate, ligand, drug, antibody, neurotransmifter or other compound normally processed or used by the body (for example, glucose) that acts as a tracer of specific physiological and biological processes.
Excessive radiation to technologists and other personnel working in the scanner room can pose a significant risk, however. Although the half-life of the radiopharmaceutical is rather short and the applied dosages are themselves not harmful to the patient, administering personnel are exposed each time they work with the radiopharmaceuticals and other contaminated materials under current procedures. Constant and repeated exposure over an extended period of time can be harmful.
A number of techniques used to reduce exposure include minimizing the time of exposure of personnel, maintaining distance between personnel and the source of radiation and shielding personnel from the source of radiation. In general, the radiopharmaceutical is typically delivered to a nuclear medicine facility from another facility equipped with a cyclotron in, for example, a lead-shielded container. Often, the radiopharmaceutical is manually drawn from such containers into a shielded syringe. See, for example, U.S. Pat. No. 5,927,351 disclosing a drawing station for handling radiopharmaceuticals for use in syringes. Remote injection mechanisms can also be used to maintain distance between the operator and the radiopharmaceutical. See, for example, U.S. Pat. No. 5,514,071, disclosing an apparatus for remotely administering radioactive material from a lead encapsulated syringe.
In one procedure, the radiopharmaceutical is injected into tubing that is coiled within a lead container. Typically, the shielded syringe used to inject the radiopharmaceutical is disconnected and replaced by a larger syringe, filled in most cases with saline, for injection into the body and flush. By emptying the second syringe, the radiopharmaceutical is flushed through the shielded, coiled tubing in the container and injected into the person, to be scanned. An excess volume of saline supplies a flushing function.
Although substantial effort is made to reduce exposure of administering and other personnel to harmful radiation, some exposure is experienced under current procedures. Being in the injection room longer than necessary is thus to be avoided. Moreover, the cumulative radiation exposure resulting from multiple injection procedures must be closely monitored to avoid overexposure. Indeed, personnel that administer radiopharmaceuticals are typically periodically rotated out of such duties to reduce the risk of overexposure.
In addition to the difficulties introduced by the hazardous nature of radiopharmaceuticals, the short half-lives of such radiopharmaceutical further complicate the administration a proper dosage to a patient. As discussed above, initial calibration of radioactivity is often made and the injection is then timed so that a dose of the desired level of radioactivity to the body is delivered (as calculated from the half-life of the radiopharmaceutical). See, for example, U.S. Pat. No. 4,472,403 in which a motor driven syringe is controlled to inject a quantity of a radiopharmaceutical stored in the syringe by calculating the injection quantity based upon the half-life of the radiopharmaceutical and the delay before injection.
Radiation detectors have also been placed upon syringe shields and in line with the radiopharmaceutical delivery system. For example, U.S. Pat. No. 4,401,108 discloses a syringe loading shield for use during drawing, calibration and injection of radiopharmaceuticals. The syringe shield includes a radiation detector for detecting and calibrating the radioactive dosage of the radiopharmaceutical drawn into the syringe. U.S. Pat. Nos. 4,562,829 and 4,585,009 disclose strontium-rubidium infusion systems and a dosimetry system for use therein. The infusion system includes a generator of the strontium-rubidium radiopharmaceutical in fluid connection with syringe for supplying pressurized saline. Saline pumped through the strontium-rubidium generator exits the generator either to the patient or to waste collection. Tubing in line between the generator and the patient passes in front of a dosimetry probe to count the number of disintegrations which occur. As the flow rate through the tubing is known, it is possible to measure the total activity delivered to the patient (for example, in milliCuries). Likewise, radiation measurements have been made upon blood flowing through the patient. For example, U.S. Pat. No. 4,409,966 discloses shunting of blood flow from a patient through a radiation detector.
The danger to administering personnel and other difficulties that arise from the nature of hazardous pharmaceuticals such as radiopharmaceuticals often affect the quality and safety of the injection procedure. For example, given the care that must be taken to prevent radiation overexposure (including limiting the duration of injection procedures), the concern with properly timing an injection and the need to prevent the creation of radioactive wastes, it is often difficult to properly eliminate air from all fluid paths before an injection begins.
It is thus very desirable to develop devices, systems and methods through which toxic or hazardous pharmaceuticals (far example, radiopharmaceuticals) can be administered in controlled manner to enhance their effectiveness and patient safety, while reducing exposure of administering personnel to such hazardous pharmaceuticals.